南黄海中部MIS6期以来沉积物稀土元素组成及其物源指示意义

Rare earth element composition and provenance implication of sediments in the Central South Yellow Sea since MIS6

  • 摘要: 对南黄海中部SYSC-1孔0~30 m段岩芯稀土元素(REE)和粒度进行分析,结合年代测定,研究了沉积物REE组成特征及其影响因素,并对其物质来源变化进行了探讨。结果表明,∑REE含量为111.66~231.12 μg/g,垂向分布变化较大,均值与中国黄土∑REE均值比较接近。∑REE与粒度变化有一定的相关性,但(La/Yb)N、(Gd/Yb)N和(δEu)N等参数受粒级影响较小。稀土元素分异参数有效示踪了物质来源,与周边河流对比发现,SYSC-1孔沉积物(La/Yb)N和(δEu)N散点图分布位置与黄河和长江较为一致,而与朝鲜半岛河流有明显不同。REE判别函数(DF)的物源区分结果表明,钻孔MIS6期经历了一次大的物源转换,沉积物由长江源(27.98~30 m)转为黄河源(24.24~27.98 m)。MIS5.5—MIS5.1期间(24.24~16.98 m)发育了浅水陆架冷水团沉积,主要是长江源细颗粒沉积物被古黄海暖流由南往北携带而来,并在冷涡区附近沉积下来。MIS5.1—MIS1期间(16.98~3 m)的低海平面时间较长,主要发育了一套滨浅海相-河口/潮坪相-三角洲相沉积,随着海平面急剧下降,陆架可容纳空间缩小,导致黄河、长江入海口向陆架区移动,黄河沉积物质控制了钻孔所处的南黄海北部区域。MIS1中晚期,山东半岛沿岸流的形成将黄河沉积物质主要控制在南黄海西部附近海域,而黄海暖流将济州岛西南部泥质区的长江源细颗粒物质搬运至SYSC-1孔附近的冷涡区沉积下来。总体来说,MIS6期以来南黄海中部海域沉积演化是西太平洋边缘海河海相互作用的一个典型范例,海平面波动和海洋环流变化在物源转换过程中发挥了重要作用。

     

    Abstract: Rare earth elements (REE) and grain size in the 0~30 m section of Core SYSC-1 sediments taken from the Central South Yellow Sea were analyzed. Combined with geochronic age dated, the composition characteristics and influencing factors of REE in sediments were studied, and the changes in their material sources were discussed. The vertical distribution of ∑REE varied greatly from 111.66 to 231.12μg/g, and the average value is similar to loess REE in China. A certain correlation between ∑REE and grain size variation was revealed. The value of (La/Yb)N, (Gd/Yb)N, and (δEu)N were less affected by particle size, which effectively reflected the provenance of sediments. Compared with the sediments of surrounding rivers, the distribution of (La/Yb)N and (δEu)N in scatter map are close to those of the Yellow River and the Yangtze River, but significantly different from those of the rivers in the Korean Peninsula. The provenance results of REE discriminant function (DF) show that the borehole experienced a sudden change in provenance during MIS6 from the Yangtze River source (27.98~30 m) to the Yellow River source (24.24~27.98m). During the MIS5.5—MIS5.1, shallow shelf cold water mass deposits (24.24~16.98 m) were developed. They were mainly composed of fine-grained sediments from the source of the Yangtze River, which were carried out northward by the ancient Yellow Sea warm current, and deposited near the cold vortex area. During the low sea level period from MIS5.1 to MIS1 (16.98~3 m), a set of littoral and shallow sea, estuarine/tidal flat and delta deposits were mainly developed. With the rapid decrease of sea level, the shelf accommodation space was reduced, which led to the shift of estuaries of the Yellow River and the Yangtze River towards shelf area, and the Yellow River sediments controlled the northern area of the South Yellow Sea. In the middle and late MIS1, the formation of the Shandong Peninsula coastal current mainly confined the Yellow River sediments to the western part of the South Yellow Sea, while the Yellow Sea warm current transported the fine particles of the Yangtze River source to the cold vortex area near the core SYSC-1 in the southwest of Jeju Island. In general, the sedimentary evolution of the central area of the South Yellow Sea since MIS6 is a good example of interaction between sea and river in the western Pacific margin. Sea level fluctuations and ocean circulation changes play an important role in the change of provenance.

     

/

返回文章
返回